It has been 15 years since 9/11, and yes, the shock has gone along with flag-waving national unity. But no one who was around then can forget that day, and no one who is around now should forget that we are still faced with insanely barbaric terrorists who want as many more such days as they can contrive.

The danger has been played down some lately. Secretary of State John Kerry suggested in a speech that news outlets should maybe tone down their reporting of catastrophic killings around the world, and President Barack Obama assures us that the Islamic State will be contained and something else -- that we are not faced with an "existential" threat, meaning that our country will not be wiped out.

While we don't want to go around shivering, shaking and thinking up new ways to squeeze relaxation and happiness out of our lives, we do want to be realistic. Thanks to improved intelligence and aggressiveness, we thwarted a number of plots here and quieted things down some for a period, but there have lately been catastrophic killings around the world and there is something else to worry about. That's bioterrorism.

The National Security Council once said a biological attack could conceivably kill hundreds of thousands of people and cost the country $1 trillion. A Blue Ribbon Study Panel late last year said we are likely to be hit and, despite spending tens of billions of dollars on the issue, are not prepared to contain a contagious outbreak. The Islamic State has said it fully intends to come at us with bioweapons.

Then there's terror-sponsoring Iran. It entered into an agreement to delay the production of nuclear weapons and gave up some materials lengthening how long it would take them to create bombs by some months. The Obama administration's idea was that we were getting friendlier with the Iranians when in fact the nation kidnapped some of our military men, has set off missiles and has screeched what a satanic horror we are at every opportunity. It has lately been learned we paid a $400 million ransom to get hostages back, and yes, it was a ransom.

What we are talking about here is possibly having nukes in the hands of the terroristic someday, and that has existential implications. Many forces have been at play, but let's consider an Obama legacy that, on one side includes the skillful use of drones and the assassination of Osama bin Laden, and on the other requires the patience of making a long list.

A few of the items: mishandling the Syrian crisis in a half dozen different ways, withdrawing troops from Iraq and the destabilizing of Libya. All the above have aided the Islamic State in its vicious emergence and such deeds as sending killers to San Bernardino, Calif., and elsewhere around the world.

The Islamic State must be eliminated from the face of the Earth, but let's not suppose that would be the end of radical Islamic terror. Some thought getting rid of al-Qaida would do the job, and we have indeed weakened it, but its loss was the Islamic State's gain.

Back in the 1950s, the philosopher Eric Hoffer showed how frustrated young men will often find sacrificial purpose in life by joining violent, hateful, fanatical mass movements. In this case, the movement is radical Islam that manifests itself in a variety of different groups. Those signing up see themselves partaking in a divinely ordained heritage under which they will eventually conquer the world and save it through Sharia law. That includes demolishing the United States.

Peaceful Muslims, which is to say, most Muslims, must reach out to these young jihadists and try to convert them to different understandings, and we in the United States should remember what we learned on 9/11, stand together, prepare with more than money and fight back, understanding that it won't be over in a day.